Autographa gamma L Silver y moth

This moth is a notorious migrant, and populations spread northwards and westwards each year from Mediterranean areas, where the pest is endemic. The larvae attack various glasshouse and outdoor plants, including brassicas, celery, field bean, lettuce, linseed, pea, potato and strawberry. Defoliation is usually the main problem but frass pellets accumulating between the leaves of infested lettuce plants are also often an important problem.

BIOLOGY

The first immigrants usually arrive in northern Europe in May, but can sometimes occur much earlier. Eggs are laid singly or in small groups on various foodplants and they hatch 1-2 weeks later. Larvae feed for about a month before pupating, each in a flimsy silken cocoon between leaves. Adults appear within about 2 weeks and often fly during sunny weather, to feed on nectar from various flowers. A second, and sometimes a third, generation may be completed during the summer and autumn. However, although capable of breeding continuously in heated glasshouses, outdoor populations in the British Isles are unable to survive the winter and autumn-reared adults usually migrate southwards, back to more favourable breeding grounds.

DESCRIPTION

Adult 35-45 mm wingspan; forewings greyish-brown to velvet-black, suffused with whitish-grey, often tinged with purplish, and bearing a silver, y-shaped mark (Fig. 319); hindwings light brown with a darker border. Larva up to 45 mm long; body varying from green to blackish-green, with a whitish or yellowish spiracular line, an often dark dorsal stripe and pale wavy lines along the back; three pairs of abdominal prolegs;

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